2.2. Demagnetization Measurements
To clean the secondary magnetizations from the sedimentary samples, we applied a stepwise alternative field (AF) demagnetization method in Pruhonice Paleomagnetism Laboratory of Czech Academy of Sciences. This method was carried out using a 2G Enterprises Cryogenic Magnetometer on 44 samples divided into 3 different sequences. The first sequence was 17 samples (13_0P, 10_5P, 09_8P, 08_5P, 05_9P, 03_8P, 01_2P, 01_2M, 03_5M, 05_8M, 08_2M, 10_0M, 13_0M, 15_0M, 17_2M, 19_2M, 22_0M) where we demagnetized at 1 mT intervals between 0-49 mT and 10 mT intervals between 50-100 mT. The second sequence was 14 samples (12_0P, 07_1P, 04_2P, 01_5P, 01_0M, 02_7M, 05_6M, 08_0M, 10_5M, 12_7M, 15_4M, 17_9M, 20_1M, 22_5M) where we demagnetized at 2 mT intervals between 0-48 mT and 10 mT intervals between 50-100 mT. The third sequence was 13 samples (10_0P, 07_7M, 05_6P, 03_0P, 00_2P, 01_8M, 04_2M, 06_2M, 09_1M, 12_8M, 14_5M, 17_0M, 21_5M) and we demagnetized at 0.5 mT intervals between 0-39.5 mT and 10 mT intervals between 40-100 mT. Demagnetization data was interpreted by using Remasoft software which was written by Agico Company (Chadima and Hrouda, 2009).
Characteristic remanent magnetization (ChRM) directions and maximum angular deviation (MAD) values were determined from principal component analysis (PCA) (Kirschvink 1980) on Zijderveld diagram (Zijderveld, 1967). Virtual geomagnetic pole’s (VGP’s) latitudes and longtitudes were calculated using PMGSC software by Randy Enkin. Table 1 shows the data of alternative field demagnetization for each individual sample. Two examples of alternative field demagnetization method for Matuyama and Brunhes sections of the samples with changes of declination, inclination angles and remanent magnetization intensity step by step are given in Figure 4. Rest of the samples are in the supplementary table S1 and table S2 containing supplementary Figures. Maximum angular deviation (MAD) changes of this study and comparisons with previous studies (Okada et al., 2017; Sagnotti et al., 2014) are shown in Figure 5.
Table 1: Alternative field demagnetization, virtual geomagnetic pole (VGP) data and Matuyama-Brunhes magnetic reversal scale for this study. Minus (-) values for virtual geomagnetic pole (VGP) latitudes and longtitudes indicate southern and western hemisphere. MAD: maximum angular deviation, φp: VGP latitude, λp: VGP longtitude.